Unit Testing


Much of this page documents the current development version of Nevow’s testing features, not the current release version. Make sure you are using the right version of the code if you attempt to make use of this documentation.

Divmod uses the stand-alone JavaScript interpreter SpiderMonkey to run unit tests on some portions of our JavaScript sources. You can find several examples in the Divmod repository.

These unit tests are valuable: they reveal simple errors, provide a kind of documentation as to the purpose of various functions, and ensure that the code is exercised in as much isolation as is possible. However, they are not all-encompassing. After all, they aren’t even executed by the same runtime that will be used by any user to execute them.

nit can also be used for unit testing (see below).

Functional Testing

To account for this, Nevow provides nit, a runner for tests which are designed to be run by an actual browser. Nit tests are placed in Python source files named with the livetest_ prefix. There are several examples of this kind of test in the Divmod repository as well.

If you are familiar with XUnit, the API presented by nit should present few surprises. The primary interface of interest to test developers is the TestCase class, which is subclassed and extended to define new tests.

Server Side

nevow.livetrial.testcase.TestCase is the base class for the server-side implementation of test methods. Subclasses of TestCase define the JavaScript class which will implement the client-side portion of test methods as well as the document which will be used to render them. TestCase is a nevow.athena.LiveFragment subclass, so it can also define methods which are exposed to the client.

A TestCase might be no more complex than the following:

from nevow.livetrial.testcase import TestCase
from nevow.athena import expose

class AdditionTestCase(TestCase):
    jsClass = 'Examples.Tests.AdditionTestCase'

Client Side

On the JavaScript side, test authors subclass Nevow.Athena.Test.TestCase and define actual test methods on it. These methods may return Deferreds if they are testing asynchronous APIs. Test methods which return a Deferred which eventually errbacks are treated as failing; those which return a Deferred which eventually callbacks are treated as succeeding. Tests which return anything other than a Deferred are also treated as succeeding, and tests which throw any error are treated as failing.

The JavaScript half of the above example might look like this:

// import Nevow.Athena.Test

Examples.Tests.AdditionTestCase = Nevow.Athena.Test.TestCase.subclass('Examples.Tests.AdditionTestCase');
    function test_integerAddition(self) {
        self.assertEqual(1 + 1, 2);

    function test_stringAddition(self) {
        self.assertEqual('a' + 'a', 'aa');

Command Line

Tests are collected into a suite automatically by the nit command line. For example, nit nevow will launch a server which runs all of Nevow’s nits. The server listens on http://localhost:8080/ by default. To run the tests, visit that URL with a browser and click the Run Tests button.